Atrial fibrillation is a well known disorder in which spurious electrical signals cause an irregular heart beat. The disorder has a well known cure known as the Maze procedure, in which a border is ablated around the sources of the spurious signals, typically in the left atrium but sometimes in the right atrium. The procedure is very commonly performed under direct vision, but difficult to perform percutaneously via a catheter because of the associated risk. Any error in navigation inside the heart can cause fatal damage. The key to a percutaneous procedure is mapping of the inside of the right and left atrium. Access to the right atrium is simple via the superior vena cava; the left atrium can be reached i) by perforating the transatrial septum, ii) via the aorta and the left ventricle or iii) via the pulmonary veins.
Prior approaches to map the inside of the atrium relied on electrical activity picked up from the atrium wall. These approaches require intimate electrical contact, not always possible because of scar tissue and deposits. These approaches may fail to accurately map the edges of the openings where the veins enter the atrium; information that is useful for correct placement of the ablation pattern. Other mapping methods, such as using an array of ultrasonic transducers, are not practical since such arrays typically will not fit through a catheter of a reasonable size (8-10 mm diameter). A superior mapping apparatus and method, that enables safe execution of the Maze and other intra-cardiac procedures is desirable.
A good survey article on the subject is: “Ablation of Atrial Fibrillation: Energy Sources and Navigation Tools: A survey” by Ruediger Becker and Wolfgang Schoels (J. of Electrocardiology, Vol 37, 2004, pp 55-61). The article includes an extensive bibliography.